2009 VSC/TRAC/AUTO-LSD snow test

The attachment you posted is the most comprehensive piece about the system, my manual doesn't have it and now it's very easy to follow the modes. You can't shut off much in 4WD!

 

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Okay, I finally took the new 2010 4 door Tacoma TRD 4WD OFF ROAD to the desert today (Ocotillo Wells) to try the new traction controls and 4WD in the sand and on hill climbs. I had a copy of NAYo2002's guide (above).

First off, the truck suspension feels much improved over my 2005, which was very soft and bottomed out with a load in the back. I added Ride Rite air springs to my 2005 to stop that problem. So, off the bat... a better feel off road, at speed.

Steep hill climb attempt... a silt covered 'dry mud' hill with some rock that steadily got steeper.

I made two runs in 2WD. First at normal settings and then with TRAC off/Auto LSD on. Neither got very far up as traction was lost in the silty dirt as soon as it got 'steep'.

So, since TRAC Off/ AUTO LSD are only features that improve 2WD performance, and are way weak if 4WD is available... let's see how many 4WD modes the Tacoma has:

1) In 4-Hi, very impressive climb up the hill... You can tell there is a difference with these limited slip differentials over the '05 with open differentials. You cannot turn TRAC or VSC off in 4 Hi... not that you would want or need to... but I tried pushing the button different ways (in Neutral, drive, etc.) with no change. All wheels with tracion pulling.

2) In 4-Lo (no TRAC or Auto LSD), lots of low end power, as with the '05... but did not climb as far up the hill as in 4-Hi ... Not impressive in this application. 1 front and 1 rear tire getting power.

3) In 4-Lo with ATRAC engaged.... WOW, way up the hill to the same approx. place as 4-Hi. As we have read, ATRAC is giving you Limited Slip Differntial action front and rear. All wheels with traction pulling.

4) In 4-Lo with REAR DIFF. LOCKED... Not as far up... I was surprised... But it was likely due to the loose dirt and the torque of 4-Lo digging... 2 rear wheels and 1 front wheel with traction pulling.

5) In 4-Lo with REAR DIFF. LOCKED AND ATRAC... Reached the high point of the hill climb. The limited slip front differential (and locked rear differential) gave the Tacoma all the climbing ability it could have... Rear 2 wheels pulling and front 2 wheels with traction pulling.

In the sand department, 4 Hi did all the driving... after trying 2 Hi normal and with TRAC OFF/ AUTO LSD ON.

Today was a quick run, as I just had to try out the new truck in the dirt. Next weekend we take it to BAJA where we will drive it on the 'bottomless' sand beaches of San Felipe that usually require tires aired down to 10-15 psi for floatation, in 4WD.

The ATRAC button was a very important addition... for those that need the most traction while in 4-Lo. I see why the excitement about cutting the wire for the pre '09 Tacomas that didn't have the ATRAC button, but did have TRAC/ AUTO LSD.

I was MOST impressed with the 4-Hi, standard TRAC mode... it was amazing all alone. 4-Lo with ATRAC may only be needed for very rocky, steep grades or extra torque in mud/ snow stuck situations...? The locking rear differential may not be so mandatory as it used to be before TRAC (Limited Slip Differentials).

More testing to come!

 

you can turn trac off in 4hi... press and hold the button while not moving.

with non trd or models you can do the yellow wire mod and you get trac in 4lo

 

I was blasting past slowpokes on the highway when I came upon about 9" of snow blown into the passing lane. I kept on the throttle and steered but the truck was understeering / pushing towards the ditch at 60 mph. The stupid VSC buzzer started singing, and the truck slowly rotated where I was steering. It was beeping for about 5 seconds, I was on throttle the whole time, as steering control diminishes in 4WD if I let off the gas, worked like a charm. It really is a useful tool once you are used to it.
I will be disconnecting the ridiculous buzzer though...

 

yes, i think that's a very important note. As scary as it is, VSC does seem to work better if you keep giving it gas.

Added: Definitely test it out for yourself in a safe environment to see what works for you though.

 

I tried... many minutes... holding the button in Neutral, Park, Drive... all while not moving. No light came on. Only in 2WD could I turn TRAC off, worked first time, every time.

What do you think? The 2010 (sold in California) is different, maybe?

 

I have an 09 but check your manual. You should be able to turn off VSC/TRAC. Put it in park and hold it for 5 seconds. Auto-LSD only works in 2wd so only indication you are going to see is a car on two squiggly lines with OFF under it.

If it still doesn't work, take it to the dealer. (After checking the manual of course.)

 

The following is from my owner's manual (2010)... I was hoping to clear some of this up... but I still need more info!

1) AUTO LSD (page 183 of the 2010 owners manual) is only for use in 2WD when one of the rear tires spins*. To activate AUTO LSD is done by pressing the VSC Off switch. The AUTO LSD light comes on. As vehicle speed increases, the VSC system will come back on and the AUTO LSD light will go off... but will come back on if speed again is reduced (page 184).

*This is an error unless there is there two levels of limited slip: TRAC and AUTO LSD? It otherwise sounds like AUTO LSD is on when the LSD is turned off, ie. LSD and No LSD... as stated below?

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2) TRAC (page 192 of the 2010 owners manual)... Clearly states that TRAC can only be turned off in 2WD mode [with a quick push of the VSC Off switch]. This to allow spinning of tires* to rock the vehicle out of a stuck situation (in 2WD).

*Here it is clear that to turn off TRAC (turn on AUTO LSD) is to take away the limited slip action and allow the tires to spin!?

>>>The AUTO LSD light that comes on when TRAC is turned off means that TRAC (which is LSD/ Limited Slip Differentials) with return 'automatically' once vehicle speed increases. On page 193 it says that AUTO LSD mode IS "automatic TRAC reactivation".
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3) VSC: On page 193, it says to turn off both TRAC and VSC you hold the VSC Off switch for more than 3 seconds, while the vehicle is stopped. TRAC and VSC will NOT come back on when vehicle speed increases. Only by pushing the switch or re-starting the engine will return the VSC and TRAC.

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Okay, my head is about to explode... Let's move on to 4WD...

4) In 4 Hi: TRAC and VSC are on... no options to turn them off (or go to AUTO LSD) to allow wheel spinning to get free from snow, sand or mud by rocking the vehicle... Only if in 2WD.

Perhaps in 4 Hi with TRAC... you will never get stuck? Maybe true...

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5) In 4 Lo: VSC system shuts off (page 180). Nothing in the manual says that the TRAC is off as well... On page 181, spinning of 4 wheels is mentioned and the reason to use A-TRAC is given. Maybe TRAC is indeed off in 4-Lo?

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6) Locking Rear Differential works in 4 Lo only and shuts off VSC and TRAC (page 186).

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7) A-TRAC 'Active Traction Control System' (page 181-2)

Works only in 4-Lo to prevent the spinning of 4 wheels.
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Can also be used with the rear differential locked, but ONLY under 3 MPH.

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I sure would like some more clarity on this... Toyota gets a D- on this manual. I am going to test the system much more in the wilds of Baja California, this weekend.

 

on some models there are two buttons there is the auto lsd button and the car with streak marks. to turn the vsc system off in 4hi you need to press and hold the out of control car button...

 

oh and btw yes trac is off in 4lo

 

Okay.... more testing in the dirt today because I was getting really stirred by the confusion and wording used.

First off... I WAS finally able to shut off the VSC in 4WD-Hi today (AUTO LSD light does not come on in 4WD). When the button (with the car and wavy skid lines) is held down for 5 seconds, then the VSC is off (also off is both TRAC and AUTO LSD). I also tried the 4-Lo, A-TRAC, and RR Diff. Lock combinations.

So, the Tacoma has tons of versatility and drive choices.

Understanding of Terminology:

SEE REVISED CHARTS BELOW...

I welcome comments, corrections, additions, clarifications!

 

Not true in 4WD high. It only transfers power, no throttle intervention.
Throttle intervention in 2L only.

ATRAC is far more similar to lockers than limited slip. TRAC is skin to a mechanical limited slip.

 

One press of VSC button turns VSC off and Auto-LSD on. Holding VSC button turns off both VSC and Auto-LSD. TRAC, IIRC, is always on.

Agree with this 100%. Love having all these tools in the toolbox.

 

Thank you for the feedback... So, TRAC in 4H works like A-TRAC or AUTO LSD (brakes only to transfer power, no throttle intervention)? What is 2L?

How does A-TRAC work more like 'lockers' if it is using brakes on one of the tires? If true, then why offer the RR locker anymore? The RR locker provides equal power to both rear tires and no braking... correct?

I only want to learn! Thanks!!

 

Thanks to Isthatahemi and others on this forum, I am getting to the facts on all the choices my Tacoma has!:

a) VSC: Vehicle Stability Control was develpoed by Bosch and uses sensors to apply brakes to wheels to keep the truck moving safely if it should go into a skid.

b) TRAC: Traction Control normally on in 2WD uses both brakes and cuts power as needed to create a limited slip differential action by braking spinning wheels and directing power to wheels with traction. In 4WD (H4), engine output is not regulated.

c) AUTO LSD (2WD Only): If TRAC is turned off in 2WD, AUTO LSD turns on and forces power to the wheel with traction by braking the spinning wheel. NO power is cut in AUTO LSD. AUTO LSD (TRAC Off only) cannot be activated in 4WD. (TRAC works the same as AUTO LSD in H4 on all 4 wheels. A-TRAC works the same as AUTO LSD in L4 on all 4 wheels).

d) A-TRAC (Active Traction Control) works only in L4 (Low Range 4WD)... works like AUTO LSD, but on all 4 wheels.

e) RR DIFF LOCK (Rear Differential Lock) works only in L4 on 4WD Tacomas. VSC and TRAC are both off when the rear differential is locked.
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Now, the various options of driving systems using the above 5 traction controls:

1) 2WD: VSC and TRAC normally active.

2) 2WD: Quick push of switch (car with wavy skid lines) turns off 'TRAC' and 'VSC', and turns on 'AUTO LSD'. Gives maximum power to tire with traction by braking spinning tire without cutting power.

3) 2WD: 5 second push of switch (while stopped) turns off all three (VSC, TRAC, AUTO LSD) for free spinning of tires. VSC will reactivate if driving over 30 MPH. This is for getting out of snow, mud, sand if spinning the tires or rocking the truck can help.

4) 4WD-Hi (H4): VSC and TRAC are both on. No engine power is cut in TRAC while in H4.

5) 4WD-Hi: 5 second push of switch (while stopped) turns off VSC and TRAC. This allows spinning of tires if needed.

6) 4WD-Lo: VSC and TRAC are both off.

7) 4WD-Lo: Push of A-TRAC button (by Cig. lighter) activates A-TRAC and forces power to the wheel with traction by braking the spinning wheel. NO power is cut in A-TRAC (just like how AUTO LSD works in 2WD).

8) 4WD-Lo: RR DIFF LOCK gives equal power to both back wheels and power to either one of the front wheels (open front differential).

9) 4WD-Lo: RR DIFF LOCK and A-TRAC activated would make the front differential limited slip by braking a spinning tire and forcing power to the tire with traction.

>>> #3, 5, 6, & 8 are open differential modes (allows tires without traction to spin, #8 the front only is open). #2, 4, 7, & 9 (AUTO LSD in H2, TRAC in H4, A-TRAC in L4) are limited slip differential modes that do not cut power.

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Charts showing the drive modes:

 

2L is a typo! I meant 2H, sorry for the confusion. Here's a comparison of TRAC and A-TRAC.

A-TRAC is quite different from TRAC. TRAC allows for a fair amount of slip. Similar to conventional LSD's, conventional LSD's are torque based, TRAC is (wheel) rpm based. When using A-TRAC, it detects not only wheel speed, but also each individual wheel's rotational position. It locks up the potentially spinning wheels, to the point that it will rotate in almost perfect unison to the other wheel on the axle. Whereas TRAC might allow a 3-5 MPH difference in wheel speed, A-TRAC will not allow even .5 MPH difference. It literally forces them to turn the same speed. I have experience with off roading locked trucks; I would take A-TRAC in all circumstances except mud-bogging. Also A-TRAC will apply abruptly, by applying full pressure, whereas TRAC ramps up to full pressure. A-TRAC also seems to exert enough resistance through the brake system to restrain very heavy throttle application; TRAC will not transfer full torque.
A-TRAC has essentially made lockers obsolete at low speeds. However, when really spinning the wheels, A-TRAC makes a real racket and doesn't seem to "keep up"; it still makes a huge difference, but is not a smooth operation.... Also, A-TRAC deactivates above 5 mph when the locker is engaged.

 

Reading through what the brakes are responsible for doing in these different traction modes makes me understand why the TRD guys said a big brake kit was not needed for non X-Runners. They must have built them beefy to withstand all the wear n tear from these multiple brake-modulated traction controls.

 

Very good explaination. Thank you!

 

Isthatahemi,

since TRAC in H4 doesn't regulate engine output (like it does in H2), is it not the same as 'A-TRAC' (which is only on in L4), or 'AUTO LSD' (which is only on in H2)?

ie. Maximum Limited Slip has three different name, depending on what drive mode you are in:

In H2: AUTO LSD (with TRAC off/ VSC off)

In H4: TRAC (only in H4 does TRAC use only brakes)

In L4: A-TRAC (AUTO LSD on all 4 wheels)

Is there any mechanical difference between the above three modes?

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To de-activate LSD (or to have open differentials to spin tires) requires:

a) 5 second hold down of switch in H2 and H4

b) Nothing in L4, normal mode is open diff. (To activated LSD, push A-TRAC switch).

Thank you.

 

My previous post explained in detail why they are different, and what the differences are.

Yes; and I also explained the difference in the rate that braking pressure is applied.
Mechanical details of note are; The A-TRAC system has a hydraulic brake booster, whereas the standard TRAC system uses vacuum. The biggest difference here is that when applying heavy throttle, there is very little engine vacuum. Therefor there is less brake pressure boost available to apply brakes and transfer torque. With A-TRAC, the brake boost function is handled independant vacuum, and subsequently, there is far greater ability to transfer torque. Wheelspeed sensors are different as well.